Arsenic speciation, oxidation and immobilization in an unsaturated soil in the presence of green synthesized iron oxide nanoparticles and humic acid

Shurui Guo; Mingqin Jiang; Jiajiang Lin; Nasreen Islam Khan; Gary Owens; Zuliang Chen

doi:10.1016/j.chemosphere.2022.137198

Arsenic speciation, oxidation and immobilization in an unsaturated soil in the presence of green synthesized iron oxide nanoparticles and humic acid

Chemosphere. 2023 Jan;311(Pt 2):137198. doi: 10.1016/j.chemosphere.2022.137198. Epub 2022 Nov 7.

Authors

Shurui Guo¹, Mingqin Jiang², Jiajiang Lin³, Nasreen Islam Khan⁴, Gary Owens⁴, Zuliang Chen⁵

Affiliations

¹ Fujian Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Fujian Normal University, Fuzhou, 350007, Fujian Province, China.
² Fujian Inspection and Research Institute for Product Quality, Fuzhou, 350002, Fujian Province, China.
³ Fujian Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Fujian Normal University, Fuzhou, 350007, Fujian Province, China. Electronic address: jjlin@fjnu.edu.cn.
⁴ Environmental Contaminants Group, Future Industries Institute, University of South Australian, Mawson Lakes, SA, 5095, Australia.
⁵ Fujian Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Fujian Normal University, Fuzhou, 350007, Fujian Province, China. Electronic address: zlchen@fjnu.edu.cn.

PMID: 36356806
DOI: 10.1016/j.chemosphere.2022.137198

Abstract

While the availability of arsenic (As) in soil is well known to be highly correlated with the presence of iron (Fe) oxides and humic acid (HA) in the soil, the relationship between Fe oxides and HA and As species in the soil is less well understood. In this study, As speciation in an unsaturated soil in the presence of external HA and green synthesized Fe oxide nanoparticles (FeNPs) showed that As(V) was mainly distributed to the specifically-bound (F2), amorphous and poorly-crystalline hydrous oxides of Fe, Al (F3) and the well-crystallized hydrous oxides of Fe and Al (F4). While As(III). This was the major component in unsaturated soil, and was mainly distributed to F4 and the residual fraction (F5). As bound to F3 and F5 was most sensitive to the addition of HA and FeNPs, while HA/FeNPs treatment increased the F3-bound As(V); however, it decreased the F5-bound As(III). Nonetheless the effect of HA on As is completely different to the HA/FeNPs treatment. The increase of As(V) in F3 resulted from F5-bound As(III) oxidation when treated by HA/FeNPs. Cyclic voltammetry confirmed that HA and Fe³⁺/Fe²⁺ redox enhanced As(III) oxidation, while FTIR revealed that HA-bound As(III) was the least available fraction in the soil. Finally, a mechanism involving a combination of HA and FeNPs was proposed for explaining the redistribution of As species in the soil.

Keywords: Arsenic; Humic acid; Iron oxide nanoparticles; Oxidation; Speciation.